1. Field of the Invention
The present invention relates to a vibration preventive coil spring mounting structure in a portable work machine, such as a chain saw, and, more particularly, to the easy mounting of the opposite ends of a vibration preventive coil spring to spring mount seats without need of troublesome works, such as welding.
2. Description of the Prior Art
A portable work machine, such as a chain saw, essentially comprises a main body including a power source, and a covering part including grip handles and arranged to surround or partially surround the outer periphery of the main body so as to support same. To suppress propagation of vibrations generated by the power source and impacts generated from the work part (saw chain and other portable power machines) to the grip handles, a plurality of vibration preventive resilient members each having a cylindrical form and made of rubber, for example, are usually interposed between the main body and the covering part so that the main body may substantially be suspended from the covering part through the vibration preventive resilient members (see Japanese Utility Model Publication No. 63-21362).
Generally, the vibration preventive resilient members are made of rubber and are interposed between the main body and the covering part. Also, at least one end of the vibration preventive resilient member is typically bonded and jointed with a fitting end metal plate to which a connecting screw member is secured.
However, the vibration preventive resilient member is adapted to connect the vibration generating source (power Source) and the stationary part (grip handles) and, therefore, there is a good possibility that the bonded portion of the fitting end metal plate will separate from the vibration preventive resilient member due to vibrations generated by the power source. Accordingly, bonding and jointing the vibration preventive resilient member and the end metal plate must be carried out with the greatest care. However, even when the bonding and jointing is done with great care, it is not infrequent that the bonded jointing portion is separated depending on the use or ambience of the work machine. In the event that one of the bonded jointing portions is separated, load acting on the bonded jointing portions of the other vibration preventive resilient members increases to make these bonded jointing portions liable to separate. Thus, eventually there arises the danger that all or almost all of the bonded jointing portions are separated and the main body separates from the covering part including the grip handles.
Under the circumstances, it is conceivable that a vibration preventive coil spring could be substituted for the vibration preventive resilient members of rubber interposed between the main body and the covering part. The use of the coil spring, however, presents a problem of how to fix the spring.
More particularly, in order to fix the coil spring to mounted parts (spring mount seats), generally, some expedients are required in which metal fittings are mounted to the opposite ends of the coil spring and jointed to the spring mount seats with screws or by welding. In another expedient, insert members made of metal or plastic are fitted in the opposite ends of the coil spring to abut against the inner periphery thereof and are fixed to the mounted parts by welding, bonding or bolting. In the above expedients, however, the assembled state between the coil spring and the metal fitting or insert member mounted thereto is unstable, resulting in possible separation of the metal fitting or insert member and in addition, considerable labor and time are required to mount the metal fittings or insert members to the mounted parts, leading to an increase in cost.
It is, therefore, an object of the present invention to provide, in a portable work machine, such as a chain saw, a vibration preventive coil spring mounting structure which, upon interposition of a vibration preventive coil spring between a main body including a power source and a covering part including grip handles and adapted to support the main body, can ensure stable,secure and easy fixing of the coil spring to spring mount seats and which is advantageous from the standpoint of reduced cost.
To accomplish the above and other objects of the invention, in a portable work machine such as a chain saw, a vibration preventive coil spring mounting structure is interposed between a main body including a power source and a covering part including grip handles and arranged to partially surround the outer periphery of the main body and support same, opposite ends of the coil spring contact spring mount seats of the main body and the covering part, respectively, cylindrical resilient fixing members are inserted into opposite ends of the coil spring and abut against inner peripheries thereof, and nut members adapted to fit into a recess at the inner end portions of the resilient fixing members. Bolts are connected to the spring mount seats and extend into opposite ends to the coil spring and threadably engaged with the nut members and tightened to compress the resilient fixing members in the axial direction and swell the fixing members in the radial direction to thereby fix the opposite ends of the coil spring to the spring mount seats.
The vibration preventive coil spring mounting structure according to the present invention constructed as above can be assembled through the procedure exemplified below.
More particularly, (i) for a single coil spring, two cylindrical resilient fixing members are prepared, each having one end to which a nut member is mounted beforehand by a suitable means such as bonding or embedding so as to prevent rotation. (ii) The resilient fixing members with nut members are inserted, headed by their side mounted with the nut member, into the opposite ends of the coil spring. (iii) The coil spring having opposite ends to which the fixing resilient members with nut members are inserted is interposed between the spring mount seats of the main body and covering part of the work machine so that the opposite ends of the coil spring contact the respective spring mount seats. (iv) The bolts (threaded) are inserted from sides of the spring mount seats opposite to the coil spring so as to be screwed into the threaded nut members and tightened.
By tightening the bolts, the nut members which are prevented from rotating are moved in the axial direction so as to approach the spring mount seats. The resilient fixing members are compressed by the axial movement of the nut members which causes the outer peripheries of the resilient members to swell in the radial direction and the swelled outer peripheral portions of the resilient members intrude into inner inter-thread gaps of the coil spring.
According to the invention, the coil spring is fixed to the spring mount seats through the medium of the resilient fixing members with nut members and the bolts.
Accordingly, the opposite ends of the coil spring are held securely by the resilient members fixing which in turn are held by the nut members and the bolts, thus ensuring that the coil spring can be prevented from departing from the spring mount seats even when subjected to very strong vibrations.
This is due to the the resilient fixing members being fitted in the opposite ends of the coil spring in a screw fashion and taking advantage of the resiliency of the fixing members to absorb the contractile movement of the coil spring.
In this manner, the coil spring can be fixed to the spring mount seats stably, securely and readily without need of troublesome work, such as welding. Also, the invention offers the advantage of cost reduction.
In addition, the vibration preventive effect due to the resilient fixing members in addition to the coil spring, can be expected, since the resilient fixing members inserted in the opposite ends of the coil spring act as a vibration preventive member.